Release array and list locks around fromlist conversions by 1ndahous3 · Pull Request #9030 · RustPython/RustPython

1ndahous3 · 2026-10-09T17:36:31Z

Summary

Prevent array.fromlist from deadlocking when __index__ or __float__ accesses the destination array or modifies the source list.
Preserve CPython's preliminary resize, live list contents, size-change errors, and rollback behavior, including buffer exports created during conversion.
Keep bulk conversion for exact builtin values. Empty input succeeds when the array has exported buffers.
Complete the fromlist follow-up to Fix array search equality and reentrant callbacks #8870.

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Summary by CodeRabbit

Bug Fixes
- Improved array.fromlist handling for bulk conversions and values that require individual conversion. Conversion failures no longer leave partially appended values when rollback is possible.
- Changes to the source list during conversion are detected, and existing error behavior is covered for index and memoryview export cases.
Tests
- Added coverage for conversion callback order, source-list and array mutations, conversion failures, and memoryview exports.

Assisted-by: Codex:gpt-6

chatgpt-codex-connector · 2026-10-09T17:36:46Z

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-09T17:44:17.242339Z	`af30f73`	PR opened

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coderabbitai · 2026-10-09T17:36:49Z

No actionable comments were generated in the recent review. 🎉

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Reviewing files that changed from the base of the PR and between f5b6526 and af30f73.

📒 Files selected for processing (2)

crates/stdlib/src/array.rs
extra_tests/snippets/stdlib_array.py

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📝 Walkthrough

Walkthrough

array.fromlist now uses bulk conversion for lists of exact built-in values and per-item conversion for other values. It checks for source-list changes during callbacks and attempts to restore the array length after errors.

Changes

Array fromlist behavior

Layer / File(s)	Summary
Array conversion and resize helpers `crates/stdlib/src/array.rs`	Bulk extension converts all items before appending. The new resize helper fills added entries with element defaults and returns `MemoryError` if capacity reservation fails. `WideChar` and `Ucs4Char` now derive `Default`.
fromlist conversion and callback handling `crates/stdlib/src/array.rs`, `extra_tests/snippets/stdlib_array.py`	`fromlist` returns for an empty list, bulk-converts lists of exact `int`, `float`, `bool`, or `str` values, and otherwise converts items individually. It detects source-list size changes and attempts to restore the original array length after errors. Tests cover callbacks, list mutation, rollback, and memoryview exports.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant Fromlist as PyArray.fromlist
  participant Source as Source list
  participant Callback as Conversion callback
  participant Storage as Array storage
  Fromlist->>Source: Read list length and items
  Fromlist->>Storage: Resize with default elements
  loop For each item
    Fromlist->>Callback: Convert item
    Callback->>Source: May change list
    Callback->>Storage: May change array
    Fromlist->>Storage: Assign converted item
  end
  Fromlist->>Source: Check list length
  Fromlist->>Storage: Attempt length rollback after error

Suggested reviewers: youknowone

Merge Risk: ⚪ Minimal · up to af30f

This change makes array.fromlist avoid lock-related deadlocks when conversion callbacks touch the array or the source list, while preserving rollback and error behavior. No concrete merge-blocking risk was identified.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 8.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 12 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title accurately identifies the main change: releasing array and list locks during `fromlist` conversions to prevent deadlocks and support callbacks that access or modify these objects.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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youknowone

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Release array and list locks around fromlist conversions

af30f73

Assisted-by: Codex:gpt-6

youknowone approved these changes Oct 10, 2026

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youknowone merged commit 11a8de1 into RustPython:main Oct 10, 2026
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1ndahous3 deleted the array_fromlist_reentry branch October 13, 2026 08:22

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Release array and list locks around fromlist conversions - #9030

Release array and list locks around fromlist conversions#9030
youknowone merged 1 commit into
RustPython:mainfrom
1ndahous3:array_fromlist_reentry

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